Untreated ends of road side barriers can be extremely hazardous if impacted since the beam of the system tends to penetrate the passager compartment (spearing) and will generally stop the vehicle abruptly. Therefore, federal regulations require a crashworthy end treatment for guard rail systems. Such end treatments must be capable of eliminating spearing and vaulting problems while maintaining full tensile strength for impacts other than axial impacts, so that the guard rail system can perform its normal vehicle redirection functions. It is also desirable that such end treatments be capable of absorbing energy of the impact.
Conventional end treatments include Energite sand-filled barrels, the GREAT system, and breakaway cable terminals. While such systems are generally acceptable for performing their desired end function, they are relatively expensive, their expense limiting their applicability in many situations. While the breakaway cable terminal system is not quite as expensive, such a system does not have good energy absorption characteristics.
The guard rail system according to the present invention is effective to prevent spearing, vaulting, or rolling of a vehicle upon axial impact of the guard rail system, yet will maintain full tensile strength for other than axial impacts, and thus provides the desired vehicle re-directional characteristics for such other impacts. The system according to the present invention also has energy absorption characteristics, and is less expensive than competing prior art systems.
The guard rail system according to the present invention includes a plurality of rail elements having characteristics for redirecting impacting vehicles (e.g. standard W-beam guard rails). A rail end is mounted to one of the rail elements and forms a termination of the plurality of rail elements. A plurality of vertical posts are provided for supporting the rail elements in a substantially horizontal position, and means are provided for mounting at least the post closest to the rail end (and preferably the four end posts) so that said post will break away upon an axial impact of the rail end but will not fail upon impact in other directions. Means are also provided for attaching the rail elements to each other in overlapping relationship so that the rail elements will move axially with respect to each other in the axial direction upon an axial impact, but will maintain full tensile strength for maintaining their re-directional characteristics upon other than axial impacts, said means comprising first bolt means and surface means of said rail elements for receiving said first bolt means. Second bolt means are also provided for attaching the rail elements to the posts. The second bolt means preferably comprise a plurality of frangible bolts for connecting the rail elements to the posts so that the rail elements will break away from the posts upon an axial impact on the rail ends but will not break away upon other than axial impacts.
The rail elements extend from the rail end in the direction of travel of vehicles along a highway with which the system is associated, and the overlapping of the rail elements is accomplished by disposing the rail element closer to the rail end of overlapping rail elements on top. The surface means of the rail elements comprises, for each bolt, a bolt receiving opening and a tang of the rail element having a root portion located closer to the rail end than the opening, and extending from the root portion to the bolt opening. The tang may be wider at its root portion than it is adjacent its respective bolt opening to allow the bolt washer to pull through on axial impacts.
Any suitable conventional arrangement may be provided for mounting the posts adjacent the rail ends so that they will break away upon an axial impact. One preferred such arrangement comprises first and second distinct post sections and coupling means for attaching the post sections together, the coupling means being those such as disclosed in copending application Ser. No. 898,892 filed Apr. 21, 1978, the disclosure of which is hereby incorporated by reference herein.
According to the invention, every other rail element may be formed with the surface means. Such rail element can be provided as inserts which may be retrofitted to conventional guard rails, and the invention is also directed to such inserts per se.
It is the primary object of the present invention to provide an effective, inexpensive, broadly applicable crashworthy end treatment for a road side barrier; and suitable rail elements therefor. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.